The invention relates to an engine arrangement comprising a noise shield and a vehicle according to the preambles of the independent claims.
It is known in the art to furnish engines of vehicles with shields of noise insulating material. Truck engines compared to passenger car engines emit more noise due to size and power of the engine. To fulfil more and more restrictive requirements with respect to emissions, the injection pressure of the engine is increased thus also increasing noise emission. On the other hand, noise shields provide a thermal insulation which may require additional cooling of the engine.
It is desirable to provide an engine arrangement which provides improved noise abatement even for engines with a high injection pressure without deteriorating cooling of the engine.
An engine arrangement is proposed for a vehicle, particularly a commercial vehicle, particularly a truck, comprising subsequently arranged and encompassed in a casing an engine block, an engine transmission and a flywheel, wherein a noise shield patch is arranged at a circumferential section of the casing overlaying not more than 75% of the circumferential section and wherein the patch is arranged predominantly beneath the casing. It is to be understood that the casing can comprise more than one housing, for instance a housing of the engine block and a flywheel housing and/or a housing of the engine transmission. The patch may even extend backwards and cover at least a portion of a clutch housing attached to the engine.
By arranging the patch predominantly underneath the casing, thermal requirements for the engine block are not deteriorated. Despite the relatively small area of the noise shield patch, the noise abatement is on a high level. The noise abating effect of the patch can be increased further if the patch can be extended to a clutch housing arranged behind the engine.
Favourably, the noise shield patch can cover an area with a high level of noise emission of the engine arrangement. Vibrations are transmitted from the piston movements in the cylinders to the crankshaft and the engine transmission. The gears in the engine transmission are excited by the vibrations and emit noise. Surprisingly it is found that it is not necessary to cover all the engine arrangement or the complete circumferential section of the engine transmission. In contradistinction to this it is sufficient to cover only a portion of the circumferential section, particularly the section beneath the engine transmission. As only a portion of the engine arrangement is covered by the patch, the cooling of the engine block is hardly affected.
According to a favourable embodiment of the invention, the patch can cover the circumferential section not more than up to an average level of a crankshaft in the engine block. It is even sufficient to cover only a bottom portion to achieve improved noise abatement of the engine.
According to a favourable embodiment of the invention, the patch can be arranged predominantly underneath a flywheel housing. Favourably, the patch covers a noise source which emits a high level of noise. This embodiment is advantageous when the engine transmission is integrated in the flywheel housing.
According to a favourable embodiment of the invention, the patch can cover a portion of the circumferential section closest to the engine transmission. The patch can be arranged below the engine transmission and/or at the side of the engine transmission. Favourably, the portion of the circumferential section closest to the engine transmission can be arranged at the side of the engine arrangement. The engine transmission is the strongest emitting noise sources in the arrangement. Thus, noise emission is effectively diminished.
According to a favourable embodiment of the invention, the patch can comprise a noise absorbing material at an inside facing the casing and a protective shield at the outside. A preferred thickness of the patch can be between 6 mm and 30 mm, depending on the most important noise frequencies. Generally, the thicker the patch is, the better is the improvement in noise abatement. However, space is very restricted around the engine arrangement. The patch can favourably be made of two sections, a noise absorber at an inner side facing the noise source and an outer shell which protects and carries the inner noise absorber. For instance, the patch can be made of a fibrous material impregnated with a resin and compacted in the outer side, e.g. by melting the resin in the fibrous material thus forming a virtually air tight shell with a sound absorbent inner side. Of course, the patch can also be laminated and consist of or comprise a shell with a noise absorber laminated to it. Preferably, an effective sound absorption material is used on the inside of the patch i.e. that portion of the patch heading the noise source.
According to a favourable embodiment of the invention, a distance between at least a portion of the patch and the casing is equal to or less than 30 mm. The portion can be a portion on the inside of the patch and/or on a perimeter of the patch. Preferably, the distance can be equal to or less than 10 mm. Expediently the patch can be arranged as close to the casing as possible or as appropriate. For instance, at least 50%, preferably 80% of the area of the patch and/or the perimeter of the patch follow closely the contours of the circumferential section covered by the patch. More particularly, the patch covers steps on the outer surface of the casing, for instance between the flywheel housing and the engine block, particularly between an oil pan beneath the engine transmission and the flywheel housing, thus providing a better noise abatement. Favourably, if the perimeter follows the casing surface closely, it is not necessary that the inner surface follows the contours of the casing so closely in the same way. The close-fitting perimeter still provides superior noise abatement, as the noise will be trapped inside the patch perimeter. Such a patch can be used for different kinds of engines, i.e. one noise patch shield can be used for different types of engines. The air gap between the perimeter and/or the patch inside can vary, but favourable can be kept as small as possible along the perimeter.
According to a favourable embodiment of the invention, the patch covers a portion of the circumferential section closest to the engine transmission. The engine transmission is the predominant noise source. The noise emitted by the engine transmission can be efficiently reduced.
According to a further favourable embodiment of the invention, the engine transmission can be provided to be arranged at a rear of the engine block in a mounted state in the vehicle.
According to a further favourable embodiment of the invention, the patch can be attached to the circumferential section with flexible connectors. Thus, vibrations are not likely to be introduced into the noise shield.
According to a further favourable embodiment of the invention, the patch can cover at least a step between an oil pan and the flywheel housing. Additionally or alternatively, the patch can cover at least a step between an oil pan beneath the engine transmission and the flywheel housing. Thus, noise emitting parts can be covered by the noise shield patch at locations which are vulnerable for emission of noise.
According to a further favourable embodiment of the invention, the engine block can be supplied with a fuel injection pressure of at least 75 MPa, favourably 100 MPa. High injection pressures induce highly dynamic forces into the engine transmission thus increasing the noise problem related to the engine transmission. Favourably, the patch can abate noise for advanced engines with high injection pressures for advanced emission standards such as Euro 5 and Euro 6
According to a further aspect of the invention, a vehicle is proposed comprising an engine arrangement according to anyone of the features described above.